1. Field of the Invention
The present invention relates to a temperature control method for use in a refrigerator which enhances cooling efficiency by promptly restoring a variation of an load temperature caused by a open door.
2. Description of the Prior Art
A conventional temperature control system for use in a refrigerator, shown in FIG. 1 comprises an alternate current (AC) power supply 17, a direct current (DC) power supply 16, a compressor 12, a compressor driving unit 11, a fan 14, a fan driving unit 13, a temperature setting unit 18 for setting a temperature inside a refrigerating compartment, a temperature detecting unit 19 for detecting a temperature inside the refrigerating compartment, a door-open detecting unit 15 for detecting an open door, and a central processing unit 10 for controlling the whole operation of a refrigerator upon receiving signals from the temperature detecting unit 15, the door-open detecting unit 19, and the temperature setting unit 18.
In the temperature control system above, when power is supplied to the AC power supply 17, the power is converted into a direct current at the DC power source 16 and supplied to the respective units so that the temperature inside the refrigerating compartment is controlled in accordance with the flow-chart, as shown in FIG. 2.
That is, when a temperature inside the refrigerating compartment is set by a user via the temperature setting unit 18, the central processing unit 10 sets a cooling operation flag (FLAG 1="1") based on the temperature which has been set by the user. At this moment, the temperature is set as a positive (+) limit temperature and a negative (-) limit temperature.
Thereafter, when the cooling operation flag (FLAG 1) is in a set state (FLAG 1="1"), the compressor 12 and the fan 14 are driven by the compressor driving unit 11 and the fan driving unit 13, respectively, upon the control of the central processing unit 10.
If the cooling operation flag (FLAG 1) is in a reset state (FLAG 1="0"), a temperature inside the refrigerating compartment which is detected at the temperature detecting unit 19 is compared with the positive (+) limit temperature which has been set in the temperature setting unit 18. If the detected temperature inside the refrigerating compartment is equal to or higher than the positive (+) limit temperature, the cooling operation flag (Flag 1) is set (FLAG 1=1") and an open door is detected. On the contrary, if the detected temperature inside the refrigerating compartment is lower than the positive (+) limit temperature, the cooling operation flag (FLAG 1) is maintained at a reset state (FLAG 1="0") and then an open door is detected.
Also, in case that a cooling operation is executed by driving the compressor 12 and the fan 14, the temperature inside the refrigerating compartment which is detected at the temperature detecting unit 19 is compared with the negative (-) limit temperature. If the detected temperature is equal to or lower than the negative (-) limit temperature, the compressor 12 and the fan 14 are stopped and the cooling operation flag (FLAG 1) is reset (FLAG 1="0") and then a door-open is detected. If the temperature inside the refrigerating compartment is higher than the negative (-) limit temperature, the compressor 12 and the fan 14 are continuously driven and an open door is detected.
The cooling operation is executed until the temperature inside the refrigerating compartment reaches to the negative (-) limit temperature, and then the compressor 12 and the fan 14 are stopped. Thereafter, when the temperature inside the refrigerating compartment rises to the positive (+) limit temperature and the cooling operation is stopped, the cooling operating flag (FLAG 1) is set to start the cooling operation.
When a closed door detected during the cooling operation is described above, it is discriminated as to whether the cooling operation flag (FLAG 1) is in a set-state (FLAG 1="1").
If an open door is detected, the fan 14 is turned off and waiting until closed door is detected. Thereafter, when closed door is detected, the cooling operation flag (FLAG 1) is set (FLAG 1="1") and then the operation of refrigerator is controlled by repeating the above-mentioned procedures.
At this moment, positive (+) and negative (-) deviations are given to the set temperature in order to prevent frequent start/stop of the compressor 12 and other units and the operation of the refrigerator is controlled so that the temperature is maintained between the positive (+) and negative (-) deviations. And, when the temperature inside the refrigerating compartment reaches the negative (-) limit temperature (t3' in FIG. 3), the central processing unit 10 stops the compressor 12 and the fan 14 and the resets the cooling operation flag until the temperature inside the refrigerating compartment rises to the positive (+) limit temperature, thereafter executing an open door detecting step.
In such a conventional temperature control method for a refrigerator, when an open door is not detected, as shown in FIG. 3, a cooling operation is started at a point t2' in which a temperature inside the refrigerating compartment reaches the positive (+) limit temperature and the cooling operation is stopped at a point t3' in which the temperature inside the refrigerating compartment reaches the negative (-) limit temperature. As a result, a load temperature is maintained between a temperature which has been set by a user and a positive (+) limit temperature. The load represents food to be retrigerated.
After the door is opened (t1 in FIG. 3) a cooling operation is started again at the point t2 that the door is closed, thereafter the cooling operation is stopped at the point t3 that the temperature inside the refrigerating compartment goes down to the negative (-) limit temperature.
When the door is opened at the point t1 of FIG. 3, a closed door is awaited and the fan 14 is stopped. At this moment, the temperature inside the refrigerating compartment and the load temperature rise abruptly (t1-t2 in FIG. 3).
Thereafter, when a closed door is detected, the refrigerating compartment is cooled to the negative (-) limit temperature. At this moment, the cooling operation is stopped irrespective of whether the load temperature reaches the negative (-) limit temperature and when the temperature inside the refrigerating compartment rises again up to the positive (+) limit temperature (point t2'), the cooling operation is started again.
In the case where the door is opened for a long time, the temperature inside the refrigerating compartment and the load temperature rise in a quickly so that a cooling operation is started again and then the cooling operation is stopped (point t3) based on the temperature inside the refrigerating compartment. At this moment, the cooling operation is stopped in a state that the load temperature does not reach the desired temperature. Accordingly, the load temperature can be dropped down to the desired set temperature only when a cooling operation is started again because of an increase of the temperature inside the refrigerating compartment up to the positive (+) limit temperature.
That is, in the conventional temperature control method for use in a refrigerator, since the temperature control is executed based on the temperature inside the refrigerating compartment, it takes a relatively long time to reach a set temperature, in cases where the load temperature is high due to an open door, thereby excerting a bad influence on the load, i.e., the food to be refrigerated.